1.a*b=cos3x/2*cosx/2-sin3x/2*sinx/2=cos(3x/2+x/2)=cos2x=1/2,
2x=π/3+2kπ或者-π/3+2kπ
x=π/6+kπ或者-π/6+kπ
第二問(wèn)是什么?兩個(gè)向量的差的平方?是的第二問(wèn)是兩個(gè)向量的差的平方，幫忙寫(xiě)下過(guò)程，2.3直接寫(xiě)答案2.y=a^2+c^2-2a*c=1+4+2根號(hào)3cos3/2x-2sin3/2x=5+4sin(π/3-3/2x)=5-4sin（3/2x-π/3)y的最小正周期是2π/3*2=4/3π增區(qū)間就是π/2+2kπ<=3/2x-π/3<=3/2π+2kπ5/9π+4/3kπ<=x<=11/9π+4/3kπ對(duì)稱(chēng)軸是3/2x-π/3=π/2+kπ，x=5/9π+2/3kπ